System of polarizing relays



Nov. 21, 1950 His Attorney.

Patented Nov. 21, 1950 SYSTEM F POLARIZING RELAYS Andrew J. McConnell, Delmar, N. Y., assigner to General Electric Company, a corporation of New York Application December 2, 1.9.48, Se1'ial,N0. 63,034

9 Claims.

This invention relates to a system of relaying and more particularly to the determination of the direction of a ground fault by means of directional ground relays.

One conventional method for determining the` direction of a ground fault by means of directional ground relays requires polarization from a current transformer in a power transformer grounded neutral.

Another conventional method of obtaining the same result is to obtain potential polarization from a source of zero-phase-sequence potential such as three phase-to-ground potential transformers with second'aries connectedin open delta.

Use of the first method depends upon having a power transformer with grounded neutral 4at the station where the directional ground relay is to be used. We shall assume for purposes of eX- plaining my invention that such a transformer is not available (as is often the case) Under such a condition the second conventional method of potential polarization may be employed. However, this method requires the installation of three phase-to-ground potential sources, such as potential transformers for polarization of the directional groundv relays. This may be a costly installation at the higher voltages, especially if two potential transformers are not already available for energization of phase relays, meters, etc.

It is an object of this invention to provide a less costly means for polarization at a station where no polarizing current or potential is available.

In general my invention comprises a system fory obtaining current or potential from a remote station having a polarization source, transmitting a quantity derived fromy that potential or current by means of carrier current to the station, in which the directional ground relay is lo- L cated, and using that derived quantity at the latter station topolarize the relay.

For an understanding of the invention` and of the improvements herein disclosed, reference should be had to the following specification, and the accompanying drawing in which Fig. 1 is a diagrammatic View of a power circuit showing the application of this` invention thereto, and Fig. 2 is a diagramma-tical view of a modification of a portion of the power circuit shown in Fig. l.

Referring to. the drawing in detail, there is shown in Fig. l a power system having stations A` and B with transrrissionl lines indicated as extending to an additional station C. At station-v A a. power transformer I having a grounded neutral 2 is available. Power is delivered by power transformer I to an electrical bus '3 of station A and thence through circuit breaker i of station A. along transmission line 5 to circuit breaker 6 of station B from which it is fed to an electrical bus i of station B and thence through circuit breaker 8 to transmission line 9 leading to station C. It is assumed that another source of ground current is present at station C or at ya point beyond.

On this power system as outlined above it is desired to provide directional ground relay protection at station B for a fault in the direction of station C, for example, at point X.

In considering the power system as thus far described, it will be noted that no means is available at station B to supply polarizing current or potential for a directional ground relay to be located at station B.

Since no power transformer is available at station B, the remaining conventional means of polarization would be the installation of three phase-to-ground potential transformers with secondaries connected in open delta, which, as previously mentioned, is costly under certain circumstances.

In order to obtain the desired protection I provide a system in which polarizing current is taken from the power transformer I of station A by means of current transformer if) electrically connected to a modulator II, which modulates a carrier current transmitter i2. Alternatively, the transformer may modulate an audio frequency wave which in turn modulates the carrier wave of transmitter I 2. The modulated carrier wave is coupled by means of a coupling capacitor I3 to transmission line 5 and received by a carrier current receiver I5 through a coupling capacitor I4 at station B. The demodulated current or voltage at the output of receiver I5 may be amplified. in an amplifier I6 where necessary and the output current of amplifier I6 is supplied to the polarizing coils Il of a directional ground relay I-B located at station B. The coil IS of directional ground relay I8 is supplied by three current transformers 2B located one in each phase between the bus I and circuit breaker 8 of station B. Line traps or filter circuits 2l are located. at each end of the transmission lines 5.

By means of this system, direction relay I8 is supplied with a polarizing means from station A.

Directional ground relay I3 will then trip breaker 8 for a fault in the direction of station C. This assumes, of course, that other breakers beyond station B have not been tripped by reason of their lower time setting and that no blocking carrier system signal has been received from station C. Relay I8 will not trip circuit breaker 8 for a fault in the direction of station A.

For the purposes of illustrating my invention, I have shown in Fig. 1 a system whereby a polarizing current quantity derivative is transmitted from a remote station to a station having no source of polarizing current or potential in order to polarize a directional ground relay. However, it will be apparent that if a zero-phasesequence potential is available at station A, a quantity derived from that voltage may be transmitted to station B in a similar manner by means of a carrier current channel to polarize a directional ground relay located at the latter station.

For example, referring to Fig. 2, a potential transformer 22 having a Y-connected grounded primary winding 23 connected to the bus 3 and an open delta connected secondary winding 24 connected to the modulator l I can be used to energize the modulator l from the transformer i in place of the current transformer ld shown in Fig. l.

By means of this system it is possible under certain circumstances to reduce to a fraction of present conventional installation costs the cost of obtaining current or potential polarization at a point remote from the polarization source.

In place of a carrier current system, other similar means for producing the same result, such as use of microwave radio transmission, may also be used.

Although an exemplary form of the invention has been shown in the accompanying drawing and described herein in detail, it is to be understood that the disclosures are not intended to be restrictive but that each may embody various modifications in detail structure without departing from the spirit oi the invention or the scope of the appended claims.

What I claim as new desire to secure by Letters Fatcnt of the United States is:

l. In an electrical power system an arrangement for polarizing a relay associated with the system in accordance with an electrical quantity derived from a. Y-connected power ransformer having a grounded neutral and located at a point remote from the relay, said'arrangement coinprising a carrier cu 1rent system, means for actuating said carrier system including a current transformer energized by the flow o current between t`ne neutral of the power transformer and ground during a fault condition, and means operable in response to the actuation of said carrier system for supplying a polarizing quantity to said relay.

2. In an electrical power system an arrangement for polarlaing a relay associated with the system in accordance with an electrical quantity derived from a Y-connected power transformer having a grounded neutral and located at a point remote from the relay, said arrangement coniprising a carrier current system, means for actuating said carrier current system from a polarizing source remote from said relay, and means operable in response to tne actuation of said carrier system for supplying a polarizing quantity to said relay.

3. In an electrical power system an arrangement for polarizing a relay associated with the system in accordance with an electrical quantity derived from a source of zero-phase-sequence potential located at a point remote from the relay, said arrangement comprising a carrier current system, means for actuating said carrier current system including means operable in response to the voltage produced from said source or" zerophase-sequence potential during a fault condition, and means operable in response to actuation of said carrier system for supplying a polarizing quantity to said relay.

4. In an electrical power system an arrangement for polarizing a relay associated with the system in accordance with an electrical quantity derived from three phase-to-neutral sources oi potential the secondaries of which are connected open delta and located at a point remote from the relay, said arrangement comprising a carrier current system, means for actuating said carrier current system including means operable in response to the voltage produced across the open delta during a fault condition, and means operable in response to actuation of said carrier system for supplying a polarizing quantity to relay.

5. In an electrical power system an arrangement for polarizing a relay associated with the system in accordance with an electrical quantity derived from three pliase--toneut1al potential transformers having their secondary windings connected in delta and located at a point remote from the relay, said arrangement comprising a carrier current system, means for act.iating said carrier system including `means operable in response to the voltage produced across the open delta during a ailt condition, and

means operable in response to actuation of said system in accordance wit'n an electrical quantity ved -from a Y-connected power transformer mg a grounded neutral and located at a point remote from the relay, said arrangement comprising a carrier current system, means lor actuating said carrier cu 1rent system in response to the new of current between tne neutral of the power transformer and ground, and means operable in response to the actuation of said carrier system for supplying a polarizing quantity to said relay.

'7. In an electrical power system an arrangement for polarizing a relay associated with the system in accordance with an electrical quantity derived from the system at a point remote from the relay, said arrangement comprising a carrier current system, means for actuating said carrier current system in response to an unbalanced voltage condition on the system occurring during a fault condition on said system, and means operable in response to actuation of said carrier system for supplying a polarizing quantity to said relay.

8. In an electrical power system an arrangement for polarizing a relay associated with the system in accordance with an electrical quantity derived from the system at a point remote from the relay, said arrangement comprising means for transmission of an electrical signal, means for actuating said signal means from a polarizing source remote from said relay, and means opel'- able in response to the actuation of said signal means for supplying a polarizing quantity to said relay.

9. In an electrical power system an arrangement for polarizing a relay associated with the system in accordance with an electrical quantity derived from the system at a point remote from the relay, said arrangement comprising a carrier current system in which a modulator modulates l, an audio tone which in turn modulates a carrier A.

current transmitter, means for actuating said? carrier current system from a polarizing source remote from said relay, and means operable in` response to the actuation of said carrier system.

for supplying a polarizing quantity to said relay.

ANDREW J. MCCONNELL.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Number Name Date Neu Sept. 22, 1908 Troger Mar. 31, 1925 Leeson June 9, 1925 Brown Nov. 10, 1931 Lehmhaus Oct. 19, 1937 Stewart Nov. 2, 1937 Seeley June 19, 1945 FOREIGN PATENTS Country Date Germany June 7, 1930 

